Streaks after sanding with U-Sand


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Old 03-29-11, 09:50 AM
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Streaks after sanding with U-Sand

Hey all,

I'm a complete newbie and this is my first attempt at refinishing hardwoods. I rented a U-Sand from the Home Depot and went over everything with 25 grit, 36, then 80. I'm doing about 1000 square feet, and after my initial sanding, I noticed streaks in the wood. I assume they're low spots. I was hoping they'd come out with each of the next passes by with fine sandpaper, but it doesn't seem to do anything. I even tried putting on the coarser grits on the U-Sand to try and level it out, but that's not working either.

Most recently, I've been trying to sand them out with a hand sander using 36 grit and 80, but haven't had much luck, plus there's so many of them, that it would probably take me a month to sand them all out. Anyone know what may have caused them and how to get them out? I wasn't planning on staining before putting a clear coat, but if it might help hide some of the marks, I'll do whatever's necessary.

I've attached some pictures.

Any help at all is greatly appreciated. Thanks in advance!





 
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Old 03-29-11, 01:57 PM
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Welcome to the forums!

I'm not familiar with HD's U-Sand Is it a big circular sander?

Pic #1 looks like you haven't sanded down far enough. I can see where 1 board is lower than the rest. The sander should do the work, are you pressing down on it as you are sanding? Generally a drum sander is used for the initial sanding but they aren't very diy friendly.
 
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Old 03-29-11, 04:12 PM
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I agree that you should keep sanding. It takes a long time. I just finished half the floors in my house (about 800 square feet of red oak) with the U-sand. I sanded from 11 a.m. to 9 p.m. without really taking a break, and I didn't finish (by finish, I mean that there was still sanding to do before I could apply poly). In total, I sanded for about 12 hours before putting down the first coat of poly, and in retrospect, I don't think I did enough sanding. Like you, I started off with the 24, which probably wasn't necessary throughout. Some of the wood was in pretty rough shape, but otherwise, I think 36 is the place to start. Are you planning to go up to 120?

I think you should expect to sand for about an hour per 75 square feet (depending on condition, etc).

I'm going to start working on the second half of the house this weekend. I'll probably start with 36, even on the rougher spots, even if it will take a long time. Then I'll probably do 60, 80, and 120 before I put down finish.
 
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Old 03-30-11, 10:07 AM
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Thanks for the replies. The U-Sand has four 6-inch orbital sanders on it. When I had it, I went over those problem spots several times with no results. That's when I started going over them by hand since I was able to get at a better angle to sand. It seems I should have gone with the drum sander, but I'd be afraid I'd rip of the floor with it, as you said it's not DIY-friendly.

I sanded for about 9 hours with 25/36 then about another 6 hours the next day with 80. You think it was a problem that I didn't use 60 in-between? Would you recommend going up to 120? The guy at the Home Depot (not that he knew what he was talking about) said 80 would be good. I'll be using an oil-based Deft finish and the can recommends sanding to 280 by hand, although I'm not sure if that's to start or between coats?

Thanks again for the replies!!
 
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Old 03-30-11, 02:03 PM
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While I've varnished/poly'd wood throughout my working life, I rarely do floors. IMO your almost always money ahead if you contract out the sanding. If sanding scratches are with the direction of the grain they won't show too bad with just poly, stain isn't as forgiving. Scratches that cross the grain will show 220 grit sandpaper is fine for sanding between coats.

I believe the sanding swirls will show if you don't sand them out first. If you wipe an area of the wood with paint thinner [mineral spirits] while the wood is still wet - that will give you an idea of what the wood will look like after you apply poly.
 
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Old 03-31-11, 02:38 PM
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I decided to try a drum sander and was very pleased with the results. I had heard horror stories of those ripping up the floor, but it was a lot easier than I expected it to be.

Thanks again for the responses!
 
 

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